Prime Minister John Key is not ruling out revising National's 2015 target for getting the Government's books back into surplus if there is a faster-than-expected slowing in the Chinese and Australian economies.

He said it was still his preference to get back into surplus at the earliest opportunity, and the advice was that this was still possible. But New Zealand was not immune from any regional downturn and that would affect the level of tax revenue the country needed to hit the 2015 target.

Mr Key was speaking at the summit of Asia-Pacific Rim economies (Apec) in Vladivostok, where concerns about the state of the powerhouse Chinese economy were aired by the region's business leaders.

The Prime Minister noted the recent falls in iron ore prices and the write-off of value in mining shares in Australia which economists are picking signals the end of the mining boom in that country.

A PricewaterhouseCoopers survey shows pessimism among business leaders to have increased over the past year.

Mr Key said it was more of a mixed picture for New Zealand.

Although the country was obviously not immune from what was happening in the region, agricultural commodity prices had risen because of drought in the Northern Hemisphere growing season.

In a speech to the business leaders meeting, Mr Key called on the US, Japan and EU countries to be bold and use the recessionary pressures on their budgets to justify cuts in trade-distorting subsidies paid to their farmers.

He said such subsidies were now "unaffordable and unsustainable".

His remarks repeated New Zealand's longstanding concerns that while some countries made much of signing free-trade agreements, they still quietly continued to subsidise their inefficient industries.